Airbag modules with dual operation are known in the above technique; i.e. airbag modules that can adopt two different states of operation from the characteristics of the vehicle's occupant when they are deployed in case of vehicle impact. For example, a first state with a small volume to protect passengers located in a forward position and a second state with a higher volume to protect passengers located in a back position.
The WO 2006/006904 patent application describes an airbag module with a double loading generator that allows the damage to be reduced that is suffered by a potentially incorrectly positioned occupant, through an active device that determines (non) activation of the second generator load based upon the degree of tension of a strap located between two opposite parts of the bag. If during its deployment, the bag quickly reaches the occupant, the strap does not tighten, and therefore the second load is not activated and consequently the bag remains in the first state. Otherwise, the strap tightens, which causes the activation of the second load, which allows the bag to reach the second state.
The U.S. Pat. No. 6,808,205 patent describes an airbag module that incorporates a combination of fabric straps sewn at different locations of the bag, which allow a deployment that is differentiated into two states.
The U.S. Pat. No. 7,111,871 patent describes an airbag module for protecting the vehicle occupant in case of a front impact, where the mentioned two states are achieved with a dual loading generator and a two-volume bag. The first state is achieved by firing the first generator load, with which the bag deploys to a small volume, assisted by some moving straps inside the bag that hold it back. The second state is achieved by firing the two generator loads, with which the bag is filled completely. At the same time, the straps move by pressure, allowing the bag to be inflated to a large volume. The decision to fire one or both generator charges takes place on the basis of the values of pre-determined variables obtained through sensor devices. For example, this decision may be made depending on the seat's position, such that the small volume is deployed if the seat is in a more forward position and the large volume if the seat is in a halfway or back position.
Those airbag modules have the basic problem that the degree of adaptiveness to the occupant is limited, since only two states of bag filling are provided. In addition, one of them requires detection mechanisms of the occupant's position, which increases its complexity and cost.
Now, the automobile industry is constantly demanding airbag modules with more capacity to adapt to the size and position of the occupant, and this invention aims to satisfy that demand.